Thalassotherapy (from the Greek word thalassa, meaning "sea") is the medical use of seawater as a form of therapy.[1] It is based on the systematic use of seawater, sea products, and shore climate.[2] The properties of seawater are believed to have beneficial effects upon the pores of the skin.[citation needed]

Some claims are made that thalassotherapy was developed in seaside towns in Brittany, France during the 19th century.[3] A particularly prominent practitioner from this era was Dr Richard Russell,[4][5][6] whose efforts have been credited with playing a role in the populist "sea side mania of the second half of the eighteenth century",[7] although broader social movements were also at play.[8] Others claim that the practice of thalassotherapy is older: "The origins of thermal baths and related treatments can be traced back to remote antiquity. Romans were firm believers in the virtues of thermalism and thalassotherapy.[2]

In thalassotherapy, trace elements of magnesium, potassium, calcium, sodium, and iodide found in seawater are believed to be absorbed through the skin. The effectiveness of this method of therapy is not widely accepted as it has not been proven scientifically. The therapy is applied in various forms, as either showers of warmed seawater, application of marine mud or of algae paste, or the inhalation of sea fog. Spas make hot seawater and provide mud and seaweed wrapping services. This type of therapy is common in the Dead Sea area.[citation needed]